Oil heater protection system

ABSTRACT

An oil heating system in which two separate sections of a heat exchanger are heated by sections of the same burner flame and have separate thermostats, either of which can shut down the system if one section clogs.

United States Patent 1191 1111 3,830,221

Hapgood 7 Aug. 20, 1974 4] 01L HEATER PROTECTION SYSTEM 2,841,337 7/1958Haugen 126/350 R x 2,846,146 3/1958 Aranl 236/20 [75] lnvemor- Hapgmd,Brooklme, 2,848,894 8 1958 Pappas 126 374 x Mass 3,118,430 [/1964Russell et 31.... 122/250 R 3,289,756 12/1966 Jaeger 165/165 [73]Asslgnee' g f Company Lexmgton 3,704,748 12 1972 Hapgood 165/125 x [22]Filed: May 1972 Primary Examin erWi1liam F. ODea 211 App} 25 14Assistant Examiner-William C. Anderson Attorney, Agent, or Firm-JosephD. Pannone; Milton D. Bartlett; Herbert W. Arnold [52] US. Cl. 126/374,165/39 [51] Int. Cl. A47j 27/00, F28f 27/02 [58] Field Of Search165/165, 39; 126/374, 351, 1 A C 126/350 73 A An oil heating system inwhich two separate sections of a heat exchanger are heated by sectionsof the same References Cited burner flame and have separate thermostats,either of UNITED STATES PATENTS which can shut down the system if onesection clogs.

1,839,392 1/1932 Humphrey 126/351 X 1,940,355 12 1933 Knapp 236/20 10 4Drawmg figures ZERO PRESSURE REGULATOR er/01D GAS INLET PATENIED M182 0I974 SHEET 10F 3 GASINLET MOTOR 'IIlE7/T RELATED CASES Application Ser.No. 10,334, filed Feb. 11, 1970, and now US. Pat. No. 3,704,748, byWilliam H. Hapgood and assigned to the same assignee as this invention,is hereby incorporated by reference and made a part of this disclosure.

BACKGROUND OF THE INVENTION In the aforereferenced copending applicationthere is disclosed a heat exchanger comprising a plurality of bodieshaving surfaces predominantly curved in all directions bonded tosections of hollow tubes to form a heat exchanger. As further disclosedtherein, such a heat exchanger produces a very uniform heating of fluidpassing through the tubular elements so that organic fluids, such ascooking oil, may be heated without regions thereof becoming overheatedand cracking to form carbon. If the fluid being heated contains foreignmaterial, such as food particles which are being cooked in the oil, suchparticles tend to clog portions of the liquid side of the heat exchangerthereby producing an overheated condition which may damage the oiland/or the heat exchanger.

SUMMARY OF THE INVENTION This invention discloses an oil heating systemin which the oil being heated flows through a plurality of paths inparallel and the oil temperature in each path is separately sensed byseparate temperature sensing elements in each of the parallel flowpaths. Changes in the temperature of the oil being heated, eitherrelative to the temperature of oil being heated in an adjacent path orrelative to a preset level indicative of an overheated condition, shutsdown the heat exchange system.

More specifically, the heat exchanger comprises a plurality of sets oftubes spaced in a cylindrical locus, each set comprising a plurality ofvertical tubes connected together in series and bonded to a plurality ofsurface extensions providing for structural rigidity between adjacenttube members. A burner structure for supplying heat, located in thecentral plenum surrounded by the tubes, directs the products ofcombustion through the spaces between a matrix formed by bodiespredominantly curved in all directions and bonded to the tubes. A pumpsupplies a liquid, such as cooking oil, to the inputs of each series oftubes and the outputs of each series of tubes supply heated oil to theheat utilization system, such as a chicken fryer.

Each of the series of tubes has at its output a temperature sensor whichprovides an indication of the heat of the oil. Since the resistance tothe flow of oil for a given temperature is made approximately the samefor each series of tubes in the heat exchanger, supplying the liquid tothe inputs of each series from a common pump insures that substantiallythe same pressure drop appears across each series of tubes. Thus, if oneof the sets of tubes begins to clog, the flow of oil through that setdecreases and the net result is an increase in the output temperature ofthe oil.

In accordance with this invention, the oil temperature outputs of theflow paths is preferably sensed by individual thermostats controllingnormally closed switches connected in series so that if the temperatureof the oil in one of the paths rises substantially above a predeterminedtemperature, the switch controlled by the thermostat in that path willopen and cause the burner to shut down.

It is contemplated that the principles of this invention may be usedwith any type of high performance heat exchanger, for example heatexchangers transferring heat at a rate in excess of 50,000 BTUs per hourper square foot of heat exchanger surface contacting the fluid beingheated, or where the fluid is being heated close to upper temperaturelimits above which damage can occur to the fluid and/or the heatexchanger. For example, in the case of cooking oil, overheating of theoil causes a charring or cracking of the oil, producing a deteriorationin taste or other quality of food product.

Such heat exchangers can, for example, be finned tube structures orconventional fin heat exchangers in which a direct flame is exposed tothe finned structure.

BRIEF DESCRIPTION OF THE DRAWINGS Other and further objects andadvantages of this invention will be apparent as the description thereofprogresses, reference being bad to the accompanying drawings wherein:

FIG. 1 illustrates an elevation view of a system embodying theinvention;

FIG. 2 illustrates a transverse sectional view of the structure shown inFIG. 1 taken along line 2-2 of FIG.

FIG. 3 illustrates a transverse sectional view of the structure shown inFIG. 1 taken along line 3-3 of FIG. 1; and

FIG. 4 illustrates a schematic diagram of a control circuit embodyingthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 through4, there is shown a heat exchange module 10 consisting of a plurality oftubes 11 spaced in a cylindrical locus and bonded together with aplurality of spheres 9 to form a heat exchanger.

A burner 13, supplied by a blower 14, is positioned in the plenum 15defined by the tubes 10. Burner 13 preferably comprises an aperturedcylindrical metal member through which a fuel-air mixture is supplied byblower 14 to the interior of the plenum 15 defined by the cylindricallyspaced tubes 11.

The fuel-air mixture is ignited by an igniter 17 which may be, forexample, a pilot light or a spark plug, and the presence or absence ofthe flame is sensed by a flame sensing device 18 which may be, forexample, a thermocouple, an electronic flame sensor, ora bimetallicswitch.

The fuel-air mixture preferably comprises gas supplied to the inputblower from a zero pressure regulator 19 through a solenoid controlvalve 20 from a gas source. The blower l2 thoroughly mixes the gas andblows it through the apertures in the burner 13 where it is ignited byigniter 17 and directed radially outwardly through the apertures betweenthe spheres 9 to transfer heat to the heat exchanger 10. The burner,igniter, flame sensor, pressure regulator and control valve, as well asthe details of the heat exchanger 10, are illustrated herein by way ofexample only, and any desired source of fuel, such as fuel oil, as wellas any desired heat exchanger configuration and igniter or flame sensorcan be used in accordance with this invention.

The zero pressure regulator 19 supplies gas to the input of the blower12 at or slightly below atmospheric pressure so that if for any reasonthe blower 12 fails and/or the solenoid valve 20 sticks, the zeropressure regulator reduces the pressure of gas to zero at the input ofthe blower 14 so that no gas leaks through the regulator into thesystem. When the blower 14 starts, on the other hand, a slight vacuum iscreated at its input causing gas to be supplied through the regulator19. In addition, variations in blower speed or other conditions, such asback pressure on a chimney vent 21 through which the products ofcombustion are vented, will produce a variation in the input vacuum ofthe blower, thereby proportionally varying the amount of fuel suppliedthrough the regulator 19 and maintaining a substantially constant and,hence, pollution-free fuelair mixture over a wide variety of operatingconditions. For additional details of such a system, reference may behad to the aforementioned copending application Ser. No. 10,334 which isnow US Pat. No. 3,704,748.

The tubes 11 are connected at their ends by means of header connectors22 into two groups of a series of tubes 11, each of said groupscomprising, for example, 12 tubes connected in series, one group of thetubes 11 defining one side of the plenum l and the other group definingthe other side of plenum 15. In accordance with the invention, theinputs of both groups of tubes are supplied through an input manifold orheader 23 with a liquid to be heated. As shown herein by way of example,pump 24 pumps oil from a vat 25 to the header 23 and thence through theheat exchanger by forcing the oil through both groups of tubes 11 inparallel to an output manifold or header 26.

Each of the two pipes 11 connected to the header 26 has a separatethermostat 28 mounted on the outside of the header with a temperaturesensing probe extending into the end of the respective tube 11 so thateach thermostat 28 responds to the temperature of the oil emerging fromthe end of that tube 11 in which its thermostatic probe 29 ispositioned. As shown here, each of the headers 23 and 26 may be, forexample, two tees having their legs attached to the tubes 11 and theiradjacent arms coupled together to form a manifold, one end of which isplugged by plugs 30.

The unplugged end of the manifold or header 23 is connected via a pipe32 to the oil pump 24 and the unplugged end of the manifold or header 26is connected to an output pipe 33 which returns heated oil to the vat25. While, as illustrated herein by way of example only, the system isused for heating oil to a temperature of, for example, 350 Fahrenheit,suitable for cooking purposes, it is contemplated that the system ofthis invention can be used to heat fluid for any desired purpose. Such asystem is particularly useful where the fluid to be heated must bemaintained below a predetermined upper temperature limit where damage tothe liquid could occur in the case of heating organic liquids.

In order to insure that no regions of the heat exchanger exceed theupper temperature limit where damage to the oil will occur in areaswhere the heat exchanger contacts the oil, the outputs of both groupsare sensed individually by the thermostatically controlled relays 28 bymeans of the individual temperature probes 29 extending into the tubes11. In the event of failure of the pump 24, or of theblockage of one ofthe groups of the heat exchanger, the flow of oil through one or bothpaths of the system is reduced to a level where the temperature of theoil arriving at either of the temperature sensing probes 29 exceeds alimit set somewhat below the maximum limit of, for example, 400Fahrenheit, to which the oil can safely be heated, and the burner isshut off in response to the thermostat whose probe 29 sensed an oiltemperature above the preset limit. Thus, it may be seen that if thefirst group of the tubes 11 has the flow therethrough slightly decreaseddue to blockage, the back pressure on the oil pump 24 will be slightlyincreased, forcing more oil through the second group of tubes andslightly reducing the temperature of the oil at the output of saidsecond group. However, the output temperature of the oil at the firstgroup of tubes will be raised due to the reduced flow of oiltherethrough, and if the blockage becomes sufficiently great, thetemperature of the oil at the output of the first group will exceed thepreset limit and the thermostat 28 sensing the first group will shut offthe burner.

An example of a control utilizing the structure of FIGS. l-3 isillustrated in FIG. 4 wherein power, for example 110 volts AC 60 cycle,supplied at input terminals 40 is connected through a master controlswitch 41 to oil pump motor 42 mechanically connected to the oil pump24. Oil pump motor 42 preferably is energized whenever power is suppliedto the system by closure of the switch 41 but, if desired, motor 42 maybe controlled, as shown, through a set of normally open contacts 43actuated by a solenoid 44 controlled by the control circuit. One side ofthe l 10 volt power supply is preferably grounded to the system, asindicated at 45, and the other side is connected through normally closedswitches 46 and 47 in thermostats 38 after passing through master switch41. Switches 46 and 47 are respectively actuated by the temperaturesensing elements 29 in the thermostats 38 so that if either of theswitches 46 or 47 opens, the portions of the control circuit fedtherethrough will be de-energized, whereas the oil pump motor 42 beingenergized from the source 40 prior to switches 46 and 47 will continueto pump if manually operated switch 39 bypassing contacts 43 is closed.

A blower motor 50 mechanically connected to blower 14 is energizedthrough the contacts 46 and 47 and the solenoid controlled normally opencontacts 51. Contacts 51 are closed by energization of a solenoid 52which is energized from a control circuit 53. Control circuit 53 derivespower from a transformer whose primary winding is connected to source 40through the contacts 46 and 47. The secondary winding of transformer 55feeds power to control circuit 53 through the normally closed contact 54of thermostat 35 which senses the temperature of the oil in the vat 25.The control circuit 53 is a conventional flame failure control circuitwhich supplies the proper ignition voltage to igniter l7 and senses thepresence or absence of the flame by the flame sensor 18 in accordancewith wellknown practice. Preferably, the volts supplied to the inputterminals 40 is reduced by transformer 55 to 24 volts or less, dependingon the particular details of the control circuit used. Thus, the voltagesupplied at the thermostat 35 attached to a vat adjacent to whichpersonnel are working is below that presenting a substantial shockhazard.

In operation, when the master switch 41 is turned on, power is suppliedthrough normally closed contacts 46 and 47, the transformer 55, andnormally closed contact 54 to control circuit 53, thereby supplyingigniting power to the igniter 17, the solenoids 52 and 44 energizing theoil pump motor 42 and the blower motor 50, and the normally closedsolenoid control valve 20. When valve 20 opens, fuel flows through theregulator 19 to the input of the blower 12 where it is mixed with airand supplied to the plenum 15 and ignited by the igniter 17. Inaccordance with well-known practice, if the control circuit 53 isenergized for a predetermined time, such as ten seconds, and a flamedoes not appear in the plenum 15 to be sensed by the flame detector 18,a timing circuit in the control circuit 53 de-energizes the solenoids 52and 44 and the valve 20, thereby shutting down the system and requiringa manual reset, for example, by means of a button illustrateddiagrammatically at 60 forre-energization of the system.

This completes the description of the invention illustrated herein.However, many modifications thereof will be apparent to persons skilledin the art without departing from the spirit and scope of thisinvention. For example, the system could be used in a closed system forheating liquids other than oil, and other types of burner systemshaving, for example, sonic atomization of fuel oil could be used.

In addition, it is contemplated that the principles of this system maybe used in a variety of control circuits, such as bridge circuits inwhich the switches 46 and 47 are replaced by resistors which vary withtemperature so that a different temperature oil supplied to theseresistors would unbalance the bridge to produce a shutdown of thesystem. The temperature at which the switches 46 and 47 open could beset at the desired temperature of the oil in the vat 25 and used tocontrol such temperature directly as well as being safety devices,thereby eliminating the need for the thermostat 35. Accordingly it iscontemplated that this invention be not limited to the particulardetails thereof disclosed herein except as defined by the appendedclaims.

What is claimed is:

1. A heat exchange system comprising:

a source of heat comprising the products of combustlon;

a heat exchanger supplied with heat from said source comprising aplurality of paths having their inputs connected to the common plenum ofa header structure for the flow of a common fluid from said headerstructure through said paths in parallel;

the surface area of said heat exchanger exposed to said products ofcombustion being substantiallygreater than the surface area of said heatexchanger defining said paths;

means for separately sensing the temperature of said fluid through atleast a plurality of said paths; and

means controlled by said sensing means for control-- ling at least partsof the operation of said system.

2. The system in accordance with claim 1 wherein said fluid comprises anorganic liquid.

3. The system in accordance with claim 1 wherein said fluid comprisescooking oil.

4. The system in accordance with claim 1 and including means for pumpingsaid fluid through said heat exchanger to a heat utilization load.

5. The system in accordance with claim 4 wherein said heat utilizationload comprises a receptacle for cooking food.

6. The system in accordance with claim 5 wherein said fluid comprisescooking oil.

7. A heat exchanger comprising:

a source of heat;

a heat exchanger comprising a plurality of paths for the flow of acommon fluid therethrough;

means for separately sensing the temperature of said fluid through atleast a plurality of said paths; means controlled by said sensing meansfor controlling at least parts of the operation of said system;

9. The system in accordance with claim 7 wherein said tubes are spacedaround a central plenum containing said source of heat which istransferred to said fluid at a rate in excess of 50,000 BTUs per hourper square foot of effective heat exchange surface contacting saidfluid.

10. The system in accordance with claim 1 wherein said source of heatcomprises a burner supplied by a blower whose input is supplied withgaseous fuel from a substantially zero pressure regulator.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,830,221 Dated August 20L 1974 Inventcflg) William H. Hapgood It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the Claims Column 6, line 21, Claim 7, delete "exchanger" and inserttherefor exchange system Signed and gealcd this thirtieth Day of September1975 [SEAL] AttESt.

RUTH C. MASON C. MARSHALL DANN Allvslmg Ofjiver Cammissz'oner of Palehrsand Trudr'marks FORM PO-105O (10-69) USCOMM-DC 60376-P69 us covsnnnsmPRINTING ornca 1959 o-aee-ssa

1. A heat exchange system comprising: a source of heat comprising theproducts of combustion; a heat exchanger supplied with heat from saidsource comprising a plurality of paths having their inputs connected tothe common plenum of a header structure for the flow of a common fluidfrom said header structure through said paths in parallel; the surfacearea of said heat exchanger exposed to said products of combustion beingsubstantially greater than the surface area of said heat exchangerdefining said paths; means for separately sensing the temperature ofsaid fluid through at least a plurality of said paths; and meanscontrolled by said sensing means for controlling at least parts of theoperation of said system.
 2. The system in accordance with claim 1wherein said fluid comprises an organic liquid.
 3. The system inaccordance with claim 1 wherein said fluid comprises cooking oil.
 4. Thesystem in accordance with claim 1 and including means for pumping saidfluid through said heat exchanger to a heat utilization load.
 5. Thesystem in accordance with claim 4 wherein said heat utilization loadcomprises a receptacle for cooking food.
 6. The system in accordancewith claim 5 wherein said fluid comprises cooking oil.
 7. A heatexchanger comprising: a source of heat; a heat exchanger comprising aplurality of paths for the flow of a common fluid therethrough; meansfor separately sensing the temperature of said fluid through at least aplurality of said paths; means controlled by said sensing means forcontrolling at least parts of the operation of said system; means forpumping said fluid through said heat exchanger to a heat utilizationload; said heat utilization load comprising a receptacle for cookingfood; said fluid comprising cooking oil; a plurality of groups oftubular elements; and the tubular elements of each of said groups beingconnected in series.
 8. The system in accordance with claim 7 whereinsaid tubular elements are spaced in a substantially cylindrical locusand are bonded to a plurality of spheres.
 9. The system in accordancewith claim 7 wherein said tubes are spaced around a central plenumcontaining said source of heat which is transferred to said fluid at arate in excess of 50,000 BTU''s per hour per square foot of effectiveheat exchange surface contacting said fluid.
 10. The system inaccordance with claim 1 wherein said source of heat comprises a burnersupplied by a blower whose input is supplied with gaseous fuel from asubstantially zero pressure regulator.